netdev - Re: [PATCH iwl-next] igc: Get rid of spurious interrupts

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Message-ID: <87ikycwyec.fsf@intel.com>
Date: Thu, 13 Jun 2024 10:22:35 -0700
From: Vinicius Costa Gomes <vinicius.gomes@...el.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Kurt Kanzenbach <kurt@...utronix.de>, Jesse Brandeburg
 <jesse.brandeburg@...el.com>, Tony Nguyen <anthony.l.nguyen@...el.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
 <pabeni@...hat.com>, Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
 intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org
Subject: Re: [PATCH iwl-next] igc: Get rid of spurious interrupts

Sebastian Andrzej Siewior <bigeasy@...utronix.de> writes:

> On 2024-06-12 12:49:21 [-0700], Vinicius Costa Gomes wrote:
>> > diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
>> > index 305e05294a26..e666739dfac7 100644
>> > --- a/drivers/net/ethernet/intel/igc/igc_main.c
>> > +++ b/drivers/net/ethernet/intel/igc/igc_main.c
>> > @@ -5811,11 +5815,23 @@ static void igc_watchdog_task(struct work_struct *work)
>> >  	if (adapter->flags & IGC_FLAG_HAS_MSIX) {
>> >  		u32 eics = 0;
>> >  
>> > -		for (i = 0; i < adapter->num_q_vectors; i++)
>> > -			eics |= adapter->q_vector[i]->eims_value;
>> > -		wr32(IGC_EICS, eics);
>> > +		for (i = 0; i < adapter->num_q_vectors; i++) {
>> > +			struct igc_ring *rx_ring = adapter->rx_ring[i];
>> > +
>> > +			if (test_bit(IGC_RING_FLAG_RX_ALLOC_FAILED, &rx_ring->flags)) {
>> 
>> Minor and optional: I guess you can replace test_bit() -> clear_bit()
>> with __test_and_clear_bit() here and below.
>
> That are two steps, first test+clear is merged into one and then __ is
> added. The former is doable but it will always lead to a write operation
> while in the common case the flag isn't set so it will be skipped.
> Adding the __ leads to an unlocked operation and I don't see how this is
> synchronized against the other writes. In fact, nobody else is doing it.
>

I just took a look at the available operations, and thought that this
one could save a few lines of code. But didn't think too deeply about
that. Thanks.

Cheers,
-- 
Vinicius